The purpose of a corner protector (e.g. on a loaded pallet), in addition to protecting the corners, is to function as a rigid vertical support at the corners of a package so that when packages are piled on top of each other, the corner protectors at their corners bear a substantial part of the load while the package itself is not subjected to a large load. Usually the corner protector is a rigid corner profile made of laminated cardboard, having two flanges at right angles to each other. The package is usually of a rectangular shape as seen from above, so it has four right-angled corners to be protected.
Previously known e.g. from specification U.S. Pat. No. 5,535,572 are devices for setting corner protectors on the corners of a package before the package is wrapped with a web of plastic film.
Previously known devices have a gripping and positioning device which grips a corner protector and moves it onto a corner of the package. A number of corner protectors are placed in a sequence in a vertical position in a storage space of a corner protector magazine. The gripping and positioning device picks one corner protector at a time from the delivery end of the storage space. The corner protector magazine is also provided with conveying means for shifting the file of corner protectors in the storage space toward the delivery end. Placed near the delivery end are arresting means to prevent the corner protectors from accidentally falling down from the delivery end.
The device presented in specification U.S. Pat. No. 5,535,572, which represents the closest state of the art with respect to the object of the present application, comprises a corner protector magazine containing a pair of conveyor belts placed at a vertical distance from each other, between which the corner protectors are held in a vertical position by their upper and lower ends by the belts. The belts, driven simultaneously at the same speed, move the corner protectors in a file toward the delivery end against a suction pad gripper, which takes the corner protector to a corner of the package.
The device of specification U.S. Pat. No. 5,535,572 is additionally provided with an arrester at the delivery end, which is designed to separate the corner protectors from each other and to prevent them from falling down from the belts before being gripped by the gripping means. Moreover, the apparatus can be adjusted to allow corner protectors of different lengths to be conveyed, by adjusting the height position of the upper conveyor in relation to the lower conveyor.
As the conveyors are in contact with the ends of the corner protectors, there is the problem that the corner protectors being moved as a file are required to be substantially equal in length. In practice, however, corner protectors commercially available are not exactly of equal length; instead, the variation in their length may be of the order of xc2x14 mm. The apparatus has a very limited range of adjustment for different corner protector lengths. In the above-mentioned apparatus, the arresters at the delivery end of the conveyors are bending springs disposed on either side of the upper and lower conveyors and crossing the path of the corner protectors so as to prevent them from falling down from the delivery end. The corner protectors are usually composed of strips of cardboard glued together on top of each other. Often some glue has flown out from between the layers, with the result that successive corner protectors in the file are glued together. A problem with this prior-art apparatus is that the weak springs can not reliably separate corner protectors thus glued together, so that when the foremost corner protector in the file is gripped by the gripping and positioning device, one or more of the corner protectors following it in the file may be picked up together with it.
The object of the invention is to eliminate the problems referred to above.
A specific object of the invention is to disclose an apparatus that involves no limitation regarding the length of the corner protectors to be handled.
A further object of the invention is to disclose an apparatus that is able to reliably separate corner protectors sticking together so that the gripping and positioning device will only take one corner protector at a time.
According to the invention, the conveying means comprise a press device driven by a first power means and arranged to be in contact with the hindmost corner protector in the file of corner protectors to move the file of corner protectors toward the delivery end and to press it so as to make it substantially compact. The arresting means comprise a gate arranged to be moved between a closed position and an open position by a second power means. In the closed position, the gate holds the file of corner protectors against the pressure applied by the press device as the foremost corner protector is leaning against the gate. In the open position of the gate, the foremost corner protector can be taken by the gripping and positioning device. Moreover, the arresting means comprise a separating tab fitted to be moved by a third power means between an arresting position and a releasing position. In the arresting position, the separating tab is between the foremost corner protector in the file and the second corner protector next in the file so as to hold the file of corner protectors against the pressure of the press device when the gate is in the open position. When the gate is in the closed position, the separating tab is in the releasing position out of the way of the corner protector so as to release the second corner protector to make it the foremost corner protector in the file so that it is pressed against the closed gate while the previously foremost corner protector is in the grip of the gripping and positioning device.
The invention is preferably applied in a system comprising a wrapping apparatus for winding a film web around a package and above-mentioned devices according to the invention for setting corner protectors on the corners of the package before its being wrapped by the wrapping apparatus. The number of such devices corresponds to the number of corners in the package.
The invention provides the advantage that the apparatus is able to handle corner protectors of widely varying lengths without having to be separately adjusted to accommodate different corner protector lengths. A further advantage of the invention is that, via interaction between a press bar, a gate and a separating tab, the apparatus can also reliably separate corner protectors sticking together. In addition to the aforementioned length tolerance, the corner protectors also have other tolerances. The thickness of the flanges may vary somewhat, and the angle between the flanges may not be exactly 90xc2x0. To ensure that the interstice between the flanges of the two foremost corner protectors will exactly coincide with the point where the separating tab is thrust into said interstice, the press device presses the corner protectors against the gate, compacting them into a tight pack, thus shaping the corner protectors so that the interstice between the flanges of the two foremost corner protectors will be exactly aligned with the separating tab.
In an embodiment of the apparatus and system, the press device comprises an elongated vertical press bar fitted to push the file of corner protectors from behind in relation to its direction of movement and a detector for detecting the pressing force of the press bar.
In an embodiment of the apparatus and system, the first power means is so controlled that it will move the press bar toward the delivery end on the basis of the compressive force detected by the detector when the compressive force falls below a predetermined limit value. Thus, the file of corner protectors remains all the time a compact pack.
In an embodiment of the apparatus and system, the gate comprises two gate parts and an upright swiveling axis for each gate part to allow them to be turned about the swiveling axis between a closed position and an open position.
In an embodiment of the apparatus and system, the gate parts are at right angles to each other when in the closed position, corresponding to the right angle of the corner protector, and substantially at an angle of about 45xc2x0 with respect to the direction of movement of the file of corner protectors.
In an embodiment of the apparatus and system, the swiveling axes are connected to each other so as to allow them to be turned by a single common second power means.
In an embodiment of the apparatus and system, the arresting device comprises two separating tabs disposed on different sides of the file of corner protectors.
In an embodiment of the apparatus and system, the separating tab is a knife-like plate. The sharp edge of the knife-like plate can easily penetrate between the flanges of the corner protectors.
In an embodiment of the apparatus and system, the third power means comprises a first shaft element which is movable in a reciprocating manner and to which the separating tab is attached, said first shaft element being designed to be movable substantially at an angle of about 45xc2x0 with respect to the direction of motion of the file of corner protectors, in a direction corresponding to the direction of the flange of the corner protector.
In an embodiment of the apparatus and system, the apparatus comprises lateral supports disposed at the height of a distance from a bottom support to support the file of corner protectors in a lateral transverse direction from opposite sides.
In an embodiment of the apparatus and system, the distance between the lateral supports is adjustable to adapt the apparatus for corner protectors of different sizes in respect of width.
In an embodiment of the apparatus and system, the detector comprises an elongated boss disposed on the front side of the press bar in the direction of movement of the file of corner protectors so that it touches the hindmost corner protector in the file, said boss being pivotally connected to one end of the press bar; a spring for forcing the boss away from the press bar in said direction of movement; a second shaft element arranged to be movable in a direction perpendicular to the longitudinal direction of the press bar; and a limit switch arranged to switch on the basis of a predetermined displacement of the second shaft element.
In an embodiment of the apparatus and system, the front side of the boss, which touches the hindmost corner protector, comprises two planar stop faces at right angles to each other, corresponding to the right angle of the corner protector.